Spinal fixation, such as lumbar sacral fusion and the correction of spinal deformity such as scoliotic curves, is a well known and frequently used medical procedure. Pedicle, lateral and oblique mounting means may be used to secure corrective spinal instrumentation to a portion of the patients' spine that has been selected for fusion by arthrodesis.
A spinal fixation system often comprises corrective spinal instrumentation which may be attached to selected vertebrae of the spine by screws, hooks and clamps. The corrective spinal instrumentation may include spinal rods or plates, which are generally installed parallel to the patients' back. The correct spinal instrumentation may further include connecting rods which extend between the spinal rods or plates. A spinal fixation system may be used to correct problems in the lumbar and thoracic portions of the spine, and may often be installed posture the spine on opposite sides of the spinous process and adjacent to the transverse process. Examples of pedicle screws and other types of fastening devices used with spinal fixation systems are shown in U.S. Pat. Nos. 4,763,644; 4,805,602; 4,887,596; 4,950,269; 5,129,388 and 5,304,179. These patents are incorporated by reference for all purposes within this Application.
When a threaded fastening device or component such as a screw, nut or bolt must be fitted into a constrained space, it is often preferable to have the fastening device or component releasably engaged with the tightening tool or handling tool. Secure, but at the same time releasable, engagement between the tightening tool and fastening device is particularly important during surgical and other medical procedures. By releasably engaging the fastening device with its associated handling tool, procedures for installing the fastening device may be simplified and the need to hold the component with one hand while using the other hand to initiate rotation or threading may be eliminated. Again, during many medical procedures such as spinal fixation, very little space is available for using more than one tightening or handling tool. Also, dropping or accidently releasing a fastening device during surgery may have serious adverse consequences.